Abstract
Although ribosomal DNA (rDNA) transcription is integral for ribosome biogenesis, the underlying regulatory mechanism in plant cell remains unclear. Here, we investigated transcription factors that are involved in nuclear and plastid rDNA transcription in a unicellular red alga Cyanidioschyzon merolae.
Chromatin immunoprecipitation (ChIP) analysis showed that RRN3, which is a key transcription factor to assemble PolI pre-initiation complex from yeast to human, specifically occupied the 18S rDNA promoter region. PolI occupation was also observed at the same region, suggesting that RRN3 function is conserved in plant cell as well as in other eukaryotes. In plastid, ChIP analyses suggested that SIG1, a RNA polymerase sigma factor, is involved in rRNA synthesis. We discuss how cell coordinates transcription of three kinds of rDNA in nucleus, plastid, and mitochondria, based on data obtained by run-on transcription analyses.
